This invention relates generally to calculators and equivalent calculating devices. More particularly, this invention relates to a novel technique for displaying a large number of menu options in a limited screen area for selection with a minimum number of key strokes.
Calculators, palmtop computers and other equivalent compact calculating devices by their nature have keyboards with a limited number of keys. To increase the number of functions, or actions, for a key, such devices often employ shift or modifier keys, one of which is pressed immediately before or simultaneously with pressing the key of interest to select the key's desired function. The various functions available for a key are usually written on the key and immediately above and below it on the keyboard in colors that correspond to the colors of modifier keys. For example, many newer calculators have a primary, or unshifted, function that is written in white on the key; a first secondary, or shifted, function written in red above the key; and a second secondary function written in blue below the key. As a practical matter, however, a key can be given no more than three or four functions because of the limited space for writing the functions on and around each key.
To further increase the number of functions a calculator can execute, menu keys ("soft keys") have been added to keyboards, typically as a row of keys placed immediately below the calculator display screen. Menus of functions may then be selected and displayed as labels above the menu keys, with each menu key associated with a label. Menu keys and the technique for displaying menus of associated labels are shown and described in U.S. Pat. No. 5,020,012, which is hereby incorporated by reference.
The drawback of present menu-based techniques is the difficulty in associating a menu option as a label with a menu key when there are more options than menu keys. For example, typically the row of menu keys consists of six keys. If the menu relates to linear units such as meters, yards, feet, inches, etc. that are to be appended to a displayed scalar value, the menu may include many more than six options. The user must then choose which six of the options he desires to be associated as labels with the menu keys.
Several prior solutions to this selection problem have been tried, each with disadvantages. A common approach is to arrange related options into a group and then display subgroups of this group corresponding in number to the number of menu keys. To access an option of the group, one then presses a key that causes the successive display of the subgroups as menu labels. After the display of a final subgroup, the calculator display re-displays a first subgroup. The disadvantage of this approach is that the user cannot see an entire group of related options at once and thus may forget where an option is located. He must also use a relatively large number of key strokes to find a desired menu option.
A second approach is to arrange the menu options in a hierarchy, where each menu label in a row represents a submenu of labels. Pressing a menu key brings up a submenu, with its options now associated as labels with the menu keys. The initial labels may indicate visually that they represent a group of related submenu options. The disadvantages of this approach include finding an acceptable grouping of functions obvious to a user and the need for a large number of key presses to find the desired option.